Selective transmission system



Jan. 22, 1935. F, TUCZEK 1,988,614

SELECTIVE TRANSMISSION SYSTEM Filed May 20, 1932 1 nna-amaoumroz :ELI a /61/ 2 .5K2 fear/ms@ f JKJ f V "Pfc/:WEE 6 INVENTOR FRANZ TUCZEK BY Z l MVC/t,

ATTORNEY Patented Jan. 22, 1935 UNITED gSTATES PATENT OFFICE SELECTIVE TRANSMISSION SYSTEM Application May 20, 1932, Serial No. 612,406

Germany 7 Claimsf 'Ihe invention is concerned with a method adapted to the electric transmission of signals or intelligence selectively to one or more receivers.

If certain radio transmissions or communications are to be sent by way of the air or conductors to ronly a single receiver or to a certain group of receivers, this, as is well known in the art, is accomplishable by the aid of selective calling or ringing in such a way that to each group of receivers a definite call, say, in the form of a pre-arranged sequence of impulses is coordinated. However. such a scheme fulfills only in a very imperfect way the requirementl that each receiver should pick up only the signals intended for it. Also, in automaticv blocking of uncalled receivers it is, generally speaking, not diiiicult to eliminate such blocking and to also receive signals and news intended for other receivers.- For purely telegraphic intelligence transmission it has for thisreason been suggested in the priorv art to modulate a radio frequency `carrier wave by an audio frequency current the tonal frequency heink keyed with a telegraph, transmitter, a distinct tonal frequency being allotted to the different receivers or groups thereof. If, then each receiver is tted with a corresponding audio frequency filter it will not be enabled readily to receive news or signals intended for other groups.

Now, a disadvantage of sucha system resides in that, whilevthe individual receiver will not require it, the employment of all receivers will require a relatively larger frequency band than is necessary for the transmission ofthe sort of signals here involved. In `other words, this method as known in the prior art willbe so much more disadvantageous, the Wider the transmission channel required rfor each individual news. While this method of vselective intelligence transmission is still useful for ordinary telegraph signals yit will become unserviceable in the case of transmissions or communications requiring a broad frequency band such as needed in picture telegraphy or television apparatus. f

'Ihe present invention discloses la new methodv for selective transmission work. The procedure according tothe invention `consists in that, in addition to the news signals proper; additional signals are transmitted which, while not required for the news'proper, are needed in order to insure correct and intelligible reception and which enable only those receivers which communication is intended to effect proper reception.

If, for certain communication work, 4supple-v mentarytsignals are anyway required for insur- April 20, 1931 ing perfect reception, such as synchronizing impulses in combination with synchronous apparatus or fading control impulses and the like, these signals could at the same time be usedffor selective transmission in that they. are `transmitted in a certain characteristic form. Equipment for this invention could also in principle be so designed to transmit, in addition to the carrier impulses of the newsV proper, impulses thatare necessary forr insuring intelligible re- 10 ception. Transmission of intelligence may be effected insuch a way that the real specific intelligence currents are transmitted inside the same or inside Vonly partly vthe same frequency range or y band, Whereas supplementalv signals for selective 15 transmission are sent out either on different frequencies coordinated to the various receivers over separate transmission channels, or else the said supplemental signals always .have thesame frequency, butare transmitted on different carrier 20 Waves whereby, if desired, ajoint radio frequency carrier'wave may. further rbe modulated.

` The present invention possesses the advantage of requiring only a comparativelysmall frequency band`- If' the supplemental or auxiliary impulses 25 are at the Sametime .used fory regulation purposes, for instance, for Athe controlof the driving motor of the receiver outfit, then the generator provided for the production of supplemental signals on different frequencies, of which, how- 30 ever,y only the frequency corresponding to the momentary transmission is sent out, is coupled with the driving means ofthe transmitter equipment. At the receiving end, suitable synchronizing means must be .provided and these may 35 consist of a lter and, in addition, such apparatus as a synchronous motor having a suitable number of poles. yIf, the auxiliary signals are of the same frequency for all-transmissions, then for` their utilization for ,synchronizing` in 'apar- 40 ticularly simple scheme the same synchronousV motors could be used both at the sending and the receiving stations. f The auxiliary signals in such a scheme could be transmitted simultaneously or alternately with the working signals, `for in- 45 stance, in picture transmission predicated upon the start-stop method always after the picture` seam.

If the selector means consist only of one filter chain vafter removal thereof, reception ofnewsf 50 not intended for a givenv receiver would still be feasible without any serious', diiiculties. This may be obviated in that jamming waves are simultaneously sentv out which are produced atirregular time intervals. `In order that unauthor- 55 ized reception may be rendered still harder it would also be possible to proceed in such a way that reception of supplemental signals or of the specific news signals, or of both, is made dependent upon the transmission of a further wave with the result that signals will be received, for instance, in a tele-typewriter, only if simultaneously a pre-arranged frequency is picked up together with a permanent signal in that arrangements are made so that all of the relays will only be caused to respond if a certain relay depending on the impulse in question has actually been operated. The same method in a similar way would be usable also in telephony work. Instead of a permanent signal, also definite impulse trains could be employed.

The method herein suggested is useful, generally speaking, for communication over the air as well as over wires. It is particularly suited for transmission over lines or networks which are used for other purposes, such as high potentiallines or lighting circuits connected with subscribers or consumers.

Further details of the invention will become clearer by referring to the following description ceiving arrangements respectively embodying the y principles of this invention in connection with picture telegraphy transmission. The auxiliary signals or impulses to insure selective. transmission serve simultaneously as synchronizing impulses between transmitter .and receiver. The frequency thereof is 50 cycles for all transmissions and by the same frequencyanother musical frequency carrier wave is modulated for each transmission. Radio transmission is effected by means of a radio frequency carrier oscillation wave suitably modulated by the news and the supplementary signals. At the receiving end the incoming radio frequency waves are first rectified, and the supplemental impulses are separated from the signals by filters.

The assumption is made that for the'transmission a frequency band of a coverage of from 30D-2400 cycles is available. For news signals,

jointly, the range between 800 and 2400 cycles is used for all transmissions, while the range 300 to 800 cycles is set aside for supplemental signals, that is to say, for ilve receiver groups for each of which a frequency between 300 and 800 cycles is se1ected,'in'the example here dealt with; group one has a selective frequency of 300 cycles, group two 400 cycles and so on.

Figure 1 shows the transmitting circuit, and

Figure 2 the receiving circuit of one of the ve receiver groups here assumed.

Referring to Figure 1, SG denotes the picture transmitter apparatus operating on a Afrequency between 800 and 2400 cycles. The picture currents are passed by way of fllter 8K1, which has a.

mission of news to the different receivers or groups of receivers. By the depression of one of the keys T1-T5 or, in case of simultaneous transmission to several receiver points, upon the depression of a plurality of said keys, the supplemental impulses for modulation are imparted to the radio frequency transmitter. Inthe example here shown only key T2 is depressed for the transmission of signals to the particular receiver equipped with filter chains SK2 400.

Device Stl has the purpose of transmitting jamming waves intended to preclude unauthorized reception, and these are initiated at instants varying from one rotation of the picture drum to the next. The same device could at the same time be used to permanently send out a definite signal that is also required to secure proper reception of news.

Referring to Figure 2, E designates the radio frequency receiver equipment in combination with a rectifier G11 which is adapted to demodulate the oscillations picked up by the receiver antenna EA. The picture impulses are fed by way of filter SKS, having a range of 800-2400 cycles wide, directly to the receiver apparatus EG, whereas the supplemental synchronizing impulses of 50 cycles with the carrier wave of 400 cycles are passed through filter SK2, are rectified by rectifier G12 and then also fed to the receiver apparatus EG. If the transmission takes place on supplemental signals which do not have a 400 cycle carrier wave then the receiving outfit will not be in position to insure proper and intelligible reception, indeed, in such case, only that particular receiving outfit will receive whose filter (8K2) is suitably tuned. If some of the receivers pertain at the same time, say, to several receiver groups adjusted to different carrier frequencies of the supplemental signals, then these receivers will have to be furnished with several lters tuned in accordance with the corresponding groups instead of with only one.

I claim:

1. In a selective multi-receiving system employing a plurality of receivers each tuned to receive a desired communication from a transmitting station, the method of operation which comprises generating at the transmitting station for each receiver a single frequency, which frequency diners. from those generated for the other receivers, modulating radio frequency carrier energy by `one of said frequencies and by a common auxiliary frequency, simultaneously modulating said carrier by a band of intelligence bearing frequencies, selectively receiving the transmitted energy on that one of the receivers which is tuned to the particular single modulating frequency selected, filtering out said single frequency and obtaining therefrom the auxiliary frequency to control said one receiver.

2. In a selective communication system employing a plurality of tuned receiving circuits, the method of communication which comprises impressing upon a radio frequency carrier wave different audio frequency characteristic frequencies modulated by synchronizing current, and a band of frequencies bearing intelligence, receiving and demodulating the transmitted energy and selectively choosing at the respective receivers only those frequencies to which the individual receivers are tuned.

3. In a selective communication system employing a plurality of tuned receiving circuits, the method of communication which comprises impressing upon a radio frequency carrier wave different continuous audio frequency waves modulated by synchronizing current, and a band of frequencies bearing intelligence, receiving and demodulating the transmitted energy and selectively choosing at the respective receivers only those frequencies to which the individual receivers are tuned.

4. In a selective communication system, a plurality of audio frequency generators each generating a different frequency. an auxiliary audiov frequency generator common to said audio frequency generators for modulating the frequencies obtained from the latter. a radio transmitter, individual connections from each of said first audio frequency generators to said radio transmitter,

and individual circuit interrupters in each of said apparatus in circuit with said radio transmitter,

said facsimile transmitting apparatus being arranged to transmit a band of audio frequencies outside the range of said other audio frequencies.

6. In a selective communication system employing a plurality of receivers each adapted to receive message waves from a single erated at the transmitting station, and selectively receiving the transmitted energy on that one of the receivers which is tuned to the particular selected characteristic frequency and filtering out the characteristic frequency to control said receiver.

7. In a selective multi-receiving system employing a plurality of receivers each timed to receive a desired communicationfrom a transmitting station, the method of operation which comprises generating at the transmitting station for each receiver a single frequency, which frequency differs from those generated for the other receivers, modulating radio frequency carrier energy by one of said frequencies and by a common auxiliary frequency, selectively receiving the transmitted energy on that one of the receivers which is tuned to the particular single modu, lating frequency selected, ltering out said singlefrequency and obtaining therefrom the auxiliary frequency to control said one receiver.

FRANZ TUCZEK. 

